Among medicines, an oral dosage form is a most frequently used dosage form, and examples of a drug composition containing an active ingredient which provides these medicines include liquid preparations, powders, fine particles, granules, tablets, and capsules. In recent years, there is provided not only a drug composition simply blended with an active ingredient but also an enteric preparation which is coated with an enteric base in order that a drug composition is protected from a low pH in stomach and an objective amount of an active ingredient can be administered without degradation, for the purpose of preventing decrease in activity of an active ingredient due to degradation and the like by the environment in a digestive tract, for example, pH in stomach. In addition, many oral dosage forms whose drug efficacy lasts with once to twice a day administration have been developed from a viewpoint of QOL improvement. Although an attempt to synthesize a compound having a kinetics such that a drug efficacy lasts by once to twice a day administration from synthetic stage of compound itself has been tried, there are not a few cases that a sustained preparation is designed and kinetics is modified by a pharmaceutical technique. As a dosage form of an oral sustained preparation, various controlled release systems such as release control by compound diffusion control with a release-controlling membrane or a matrix, release control of compound by erosion of a matrix (base), pH-dependent release control of compound, timed release control for releasing a compound after a certain lag time, and the like have been developed and applied. It is considered that the sustained release property can be further prolonged by combining control of moving rate in a digestive tract with the above release controlling systems.
For example, as a dosage form affording an enteric preparation as one embodiment of a release-controlled preparation, a combination of tablets, fine particles, granules or powders prepared by mixing an active ingredient and excipients composing a drug composition, with a base having enteric property are provided, and preferred is a preparation in which an enteric base is rapidly dissolved in a lower digestive tract including duodenum after passed through the gastric environment and an active ingredient is rapidly dissolved out. From this point of view, in the case of normal size tablets, a combination of fine particles, granules, or powders with an enteric base are more preferred since the specific surface area is increased compared to tablets. Or, in the case where formulated into tablets, downsized tablets are preferable as compared with normal tablets. In addition, when an oral preparation is administered, particularly, in an enteric preparation which is not disintegrated or dissolved in stomach, transference of a preparation from stomach to a lower digestive tract including duodenum is controlled by dynamic activity of a digestive tract and, in particular, in tablets, the transference is greatly governed by a gastric emptying time and, as a result, after administration, a time of movement to a lower digestive tract including duodenum is not constant, and therefore, appearance of blood concentration of an active ingredient is not constant. For the purpose of improving this defect and appearance of a stable blood concentration with small variation, enteric preparations such as fine particles, granules, and the like are developed. Since enteric preparations such as fine particles and granules are multiple unit preparations in which the number of particles in preparations is plural, a gastric emptying time has a small variation as a whole and, after gastric evacuation, a preparation is rapidly dissolved and an active ingredient is dissolved out, therefore, quality of remedy is improved. In addition, when a release-controlled drug composition other than enteric composition is provided, and also when there are a change in solubility in each site of digestive tract based on physicochemical property of an active ingredient and a variation in dissolution and release property from a drug composition, appearance of a stable blood level with small variation and temporal transition thereof can be provided by stably providing a distribution of movement from an esophagus to a lower digestive tract.
For example, in a preparation containing a drug having acid labile property as an active ingredient such as a benzimidazole compound having a proton pump inhibitory activity (hereinafter, referred to as PPI in some cases), an enteric coat needs to be provided. That is, since a composition containing a benzimidazole compound having PPI activity is required to be rapidly disintegrated in an intestine, it is preferred to be formulated into preparations as granules or fine particles which have a greater surface area than that of tablets and are easy to be disintegrated or dissolved rapidly, and, also in the case of tablets, it is preferable to make them into downsized tablets.
Although enteric granules or fine particles can be also prepared by coating granules or fine particles prepared by the general pharmaceutical technique with an enteric base, or by mixing an enteric base with other excipients and active ingredients, for example, they are provided by coating substantially spherical granules or fine particles prepared by adhering an active ingredient or an active ingredient and a suitable excipient to a substantially spherical core prepared from a substance available as an excipient for medicines, with an enteric base.
In addition, as the relating technical documents, EPA 277741 and U.S. Pat. No. 6,274,173 are exemplified.